This domain is found in E3 ubiquitin-protein ligases TTC3 and DZIP3 and its function is unknown. TTC3 mediates ubiquitination and degradation of phosphorylated Akt, apparently its preferable target [1]. DZIP3 is also able to bind RNA through a Lys-rich region which enhances is ubiquitination activity. It is suggested that RNA-binding proteins or ribonucleoprotein particles might be physiological targets for this enzyme, which could be important during viral infections, especially for those replicating through RNA intermediates [2]. This domain is also found in uncharacterised proteins found in viruses.

1: The E3 ligase TTC3 facilitates ubiquitination and degradation of phosphorylated Akt. Suizu F, Hiramuki Y, Okumura F, Matsuda M, Okumura AJ, Hirata N, Narita M, Kohno T, Yokota J, Bohgaki M, Obuse C, Hatakeyama S, Obata T, Noguchi M; Dev Cell. 2009;17:800-810. PMID:20059950

2: hRUL138, a novel human RNA-binding RING-H2 ubiquitin-protein ligase. Kreft SG, Nassal M; J Cell Sci. 2003;116:605-616. PMID:12538761